Since a chemical reaction process, such as organic synthesis and crystallization, requires a high precision temperature control, a double shell structure vessel is employed for a reactor, which is surrounded by a jacket allowing a heat medium to flow through as a temperature regulating unit. The heat medium is regulated at a preset temperature and circulated through the jacket to maintain the internal temperature of the reactor at a preset temperature (e.g. see Patent Document 1).    Patent Document 1: Japanese Patent Laid-Open No. 2007-127334.